Java override compareTo, Long

Question

I have a class that implements the Comparable interface. In this class I need to override compareTo method in order to sort objects by Long values.

What I don't know is how to perform is the comparison of the Long type. I get error when trying to check if value is greater than or less than another Long value. I know Long is the object of long, but have no idea how to compare two Long's.

Code sample:

public int compareTo(MyEntry<K, V> object) {
    if (this.value < object.value)
        return -1;
    if (this.value.equals(object.value))
        return 0;

    return 1;
}

Error message:

           operator < cannot be applied to V,V
if (this.value < object.value)
                       ^

V, V is Long, Long

Answer 1

Your problem is that MyEntry<K, V> doesn't tell the compiler what type of Object you're trying to compare. It doesn't know that you're comparing Long values. The best way to do this is to not worry about what type of Object you're comparing (assuming your object implements Comparable) by just using

return this.value.compareTo(object.value);

but if you want to do it manually for some reason, do this:

public int compareTo(MyEntry<K, V> object) {
    if ((Long) this.value < (Long) object.value)
        return -1;
    if (this.value.equals(object.value))
        return 0;

    return 1;
}